clarify required parallelism for scalapack
Currently, while running the Octopus with OpenMP-only parallelization it reports:
************************** Parallelization ***************************
Info: Octopus will run in *parallel*
Number of processes : 1
Number of threads per process : 18
**********************************************************************
But if the scalapack is needed, the error reads:
**************************** FATAL ERROR *****************************
*** Fatal Error (description follows)
*--------------------------------------------------------------------
* The scalapack subspace diagonalization can only be used in parallel.
*--------------------------------------------------------------------
Edited by Meisam Tabriz